Silicon and silicon germanium nanowire formation

ABSTRACT

Among other things, one or semiconductor arrangements, and techniques for forming such semiconductor arrangements are provided. For example, one or more silicon and silicon germanium stacks are utilized to form PMOS transistors comprising germanium nanowire channels and NMOS transistors comprising silicon nanowire channels. In an example, a first silicon and silicon germanium stack is oxidized to transform silicon to silicon oxide regions, which are removed to form germanium nanowire channels for PMOS transistors. In another example, silicon and germanium layers within a second silicon and silicon germanium stack are removed to form silicon nanowire channels for NMOS transistors. PMOS transistors having germanium nanowire channels and NMOS transistors having silicon nanowire channels are formed as part of a single fabrication process.

RELATED APPLICATION

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 15/463,326, titled “SILICON AND SILICON GERMANIUMNANOWIRE FORMATION” and filed on Mar. 20, 2017, which is a continuationof and claims priority to U.S. patent application Ser. No. 14/929,504,titled “SILICON AND SILICON GERMANIUM NANOWIRE FORMATION” and filed onNov. 2, 2015. U.S. patent application Ser. No. 14/929,504 is adivisional of and claims priority to U.S. patent application Ser. No.13/971,239, titled “SILICON AND SILICON GERMANIUM NANOWIRE FORMATION”and filed on Aug. 20, 2013. U.S. patent applications Ser. Nos.13/971,239, 14/929,504, and 15/463,326 are incorporated herein byreference.

BACKGROUND

A transistor, such as a FinFET transistor, comprises a source region, adrain region, and a channel region between the source region and thedrain region. The transistor comprises a gate region that controls thechannel region to operate the transistor. The gate region can be formedaround one or more surfaces of the channel region, which provides thegate region with increased control over the channel region because thetransistor can be controlled by a 3D gate area, as opposed to beingcontrolled merely by a 2D gate area associated with a 2D planartransistor.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram illustrating a method of forming asemiconductor arrangement, according to some embodiments.

FIG. 2 is an illustration of a silicon and silicon germanium stack,according to some embodiments.

FIG. 3 is an illustration of a first source region and a first drainregion, according to some embodiments.

FIG. 4 is an illustration of oxidizing a silicon and silicon germaniumstack, according to some embodiments.

FIG. 5 is an illustration of a removing silicon oxide region, accordingto some embodiments.

FIG. 6 is an illustration of a first set of nanowire transistorscomprising a gate structure formed according to a gate-all-aroundstructure, according to some embodiments.

FIG. 7 is an illustration of a first set of nanowire transistors,according to some embodiments.

FIG. 8 is an illustration of a silicon and silicon germanium stack,according to some embodiments.

FIG. 9 is an illustration of a third source region and a third drainregion, according to some embodiments.

FIG. 10 is an illustration of a third set of nanowire transistors,according to some embodiments.

FIG. 11 is an illustration of an NMOS gate height and a PMOS gateheight, according to some embodiments.

DETAILED DESCRIPTION

The claimed subject matter is now described with reference to thedrawings, wherein like reference numerals are generally used to refer tolike elements throughout. In the following description, for purposes ofexplanation, numerous specific details are set forth in order to providean understanding of the claimed subject matter. It is evident, however,that the claimed subject matter can be practiced without these specificdetails. In other instances, structures and devices are illustrated inblock diagram form in order to facilitate describing the claimed subjectmatter.

One or more semiconductor arrangements, and one or more techniques forforming such semiconductor arrangements are provided herein. Forexample, a semiconductor arrangement comprises silicon and silicongermanium stacks that are used to create germanium nanowire channels forPMOS transistors and silicon nanowire channels for NMOS transistors. Inan example, the PMOS transistors and the NMOS transistors can be formedduring a single fabrication process, such that a PMOS transistor isprotected with a hard mask while an NMOS transistor is being processed,and the NMOS transistor is protected with a hard mask while the PMOStransistor is being processed.

To form a germanium nanowire channel from the silicon and silicongermanium stack for a PMOS transistor, the silicon and silicon germaniumstack is oxidized so that the silicon is transformed into a siliconoxide region such as silicon dioxide, resulting in a germanium nanowirechannel. In an embodiment, a nanowire comprising a germanium nanowirechannel has a diameter between about 5 nm to about 15 nm. In anembodiment such a diameter is between about 15 nm to about 55 nm. In anembodiment such a diameter is between about 20 nm to about 30 nm. In anembodiment such a diameter is about 6 nm. In an embodiment, a nanowirecomprising a germanium nanowire channel has a length or defines achannel length of between about 15 nm to about 55 nm, where such achannel length is measured from a source region to a drain region of thePMOS transistor. The silicon oxide region can be removed, and a gatestructure can be formed around one or more surfaces, such as one, two,three, or all surfaces, of the germanium nanowire channel.

To form a silicon nanowire channel from a second silicon and silicongermanium stack for a NMOS transistor, a silicon germanium layer isremoved from the second silicon and silicon germanium stack to form asilicon nanowire channel. In an embodiment, a nanowire comprising asilicon nanowire channel has a diameter between about 5 nm to about 15nm. In an embodiment such a diameter is between about 15 nm to about 55nm. In an embodiment such a diameter is between about 20 nm to about 30nm. In an embodiment such a diameter is about 6 nm. In an embodiment,the silicon nanowire channel has a diameter that is equal to orsubstantially equal to a diameter of the germanium nanowire channel. Inan embodiment, the silicon nanowire channel has a diameter that islarger than a diameter of the germanium nanowire channel. In anembodiment, the silicon nanowire channel has a diameter that is betweenabout 2 nm to about 3 nm larger than a diameter of the germaniumnanowire channel. In an embodiment, the silicon nanowire channel has adiameter that is between about 20% to about 40% larger than a diameterof the germanium nanowire channel. In an embodiment, a nanowirecomprising a silicon nanowire channel has a length or defines a channellength of between about 15 nm to about 55 nm, where such a channellength is measured from a source region to a drain region of the NMOStransistor.

In this way, PMOS transistors, comprising germanium nanowire channels,and NMOS transistors, comprising silicon nanowire channels, can beformed within the semiconductor arrangement from silicon and silicongermanium stacks. In an example, the semiconductor arrangement hasimproved current, such as between about 14% to about 16% improvedcurrent for NMOS transistors and between about 13% to about 15% improvedcurrent for PMOS transistors. In an example, the semiconductorarrangement has reduced short channel effect, such as between about 6%to about 8% reduction for NMOS transistors and between about 4% to about6% reduction for PMOS transistors.

In an embodiment, a gate dielectric layer is formed around at least oneof the silicon nanowire channel or the germanium nanowire channel. In anembodiment, the gate dielectric layer comprises at least one of aninterfacial layer (IL) or a high-k dielectric layer (HK layer). In anembodiment, the IL has a thickness between about 5 A to about 15 A. Inan embodiment, the HK layer has a thickness between about 5 A to about20 A. In an embodiment, at least one of the thickness of the IL aroundthe silicon nanowire channel or the thickness of the HK layer around thesilicon nanowire channel is less than at least one of the thickness ofthe IL around the germanium nanowire channel or the thickness of the HKlayer around the germanium nanowire channel. In an embodiment, at leastone of the thickness of the IL around the silicon nanowire channel orthe thickness of the HK layer around the silicon nanowire channel isbetween about 5% to about 15% less than at least one of the thickness ofthe IL around the germanium nanowire channel or the thickness of the HKlayer around the germanium nanowire channel.

A method 100 of forming a semiconductor arrangement is illustrated inFIG. 1, and one or more semiconductor arrangements formed by such amethodology are illustrated in FIGS. 2-10. A semiconductor arrangement250 comprises a substrate 202, as illustrated in embodiment 200 of FIG.2. In an example, the substrate 202 comprises silicon, and the substrate202 is formed according to a FinFET arrangement comprising one moresilicon fins separated by isolation structures 204, such as shallowtrench isolation (STI). For example, a first fin 202 a, a second fin 202b, a third fin 202 c, and a fourth fin 202 d are formed from thesubstrate 202. In an example, an isolation structure has a depth betweenabout 60 nm to about 120 nm. In an example, a recessed space, betweenabout 50 nm to about 110 nm, is formed into the substrate 202 forformation of silicon and silicon germanium, such as through an epigrowth technique for a silicon and silicon germanium stack where an epithickness of silicon germanium is between about 5 nm to about 15 nm andan epi thickness for silicon is between about 5 nm to about 15 nm.

At 102, a silicon and silicon germanium stack is formed over thesubstrate 202, as illustrated in embodiment 200 of FIG. 2. For example,a first silicon and silicon germanium stack 220, a second silicon andsilicon germanium stack 222, or other silicon and silicon germaniumstacks not illustrated or identified are formed over the substrate 202.The first silicon and silicon germanium stack 220 comprises one or moresilicon layers and one or more silicon germanium layers. For example,the first silicon and silicon germanium stack 220 comprises a firstsilicon layer 218, a first silicon germanium layer 206, a second siliconlayer 208, a second silicon germanium layer 210, a third silicon layer212, a third silicon germanium layer 214, and a fourth silicon layer216. It is appreciated that any number of silicon layers or silicongermanium layers can be formed. In an example, a silicon germanium layercomprises between about 20% to about 50% germanium.

At 104, a first source region 302 is formed adjacent to a first side ofthe first silicon and silicon germanium stack 220, as illustrated inembodiment 300 of FIG. 3. It is appreciated that the first source region302 is illustrated by dashed lines for illustrative purposes so thatother portions of the semiconductor arrangement 250 are visible orapparent. At 106, a first drain region 304 is formed adjacent to asecond side of the first silicon and silicon germanium stack 220, asillustrated in embodiment 300 of FIG. 3. In an example of forming thefirst source region 302 and the first drain region 304, a sacrificialgate is formed, such as a polygate formed by a patterning technique,over the substrate 202 and over the first silicon and silicon germaniumstack 220. Spacers are formed, such as by a deposition technique, onsidewalls of the of the semiconductor arrangement 250. Portions of thefirst silicon and silicon germanium stack 220, corresponding to thefirst source region 302 and the first drain region 304, are removed,such as through an etching technique. Source and drain material isformed within the first source region 302 and the first drain region304, such as through an epitaxial growth technique, to create a firstsource and a first drain for a first nanowire transistor. Other sourceregions, such as a second source region 306, and drain regions, such asa second drain region 308, are formed for other nanowire transistorsthat are to be formed for the semiconductor arrangement 250.

At 108, the first silicon and silicon germanium stack 220, illustratedin embodiment 300 of FIG. 3, is oxidized 402 to form a first oxidizedstack 220 a, as illustrated in embodiment 400 of FIG. 4. In an example,the second silicon and silicon germanium stack 222, illustrated inembodiment 300 of FIG. 3, is oxidized 402 to form a second oxidizedstack 222 a, as illustrated in embodiment 400 of FIG. 4. In an example,the oxidizing 402 comprises removing a sacrificial gate, notillustrated, over the first silicon and silicon germanium stack 220 toexpose the first silicon and silicon germanium stack 220 to ambientoxygen. Oxidizing 402 the first silicon and silicon germanium stack 220transforms silicon, such as silicon of a silicon layer or silicon of asilicon germanium layer, to silicon oxide such as silicon dioxide. Forexample, the first silicon layer 218 is transformed to a first siliconoxide region 218 a. Silicon of the first silicon germanium layer 206 istransformed to silicon oxide, resulting in a first germanium nanowirechannel 206 a between the first source region 302 and the first drainregion 304. The second silicon layer 208 is transformed to a secondsilicon oxide region 208 a. Silicon of the second silicon germaniumlayer 210 is transformed into silicon oxide, resulting in a secondgermanium nanowire channel 210 a between the first source region 302 andthe first drain region 304. The third silicon layer 212 is transformedto a third silicon oxide region 212 a. Silicon of the third silicongermanium layer 214 is transformed into silicon oxide, resulting in athird germanium nanowire channel 214 a between the first source region302 and the first drain region 304. The fourth silicon layer 216 istransformed to a fourth silicon oxide region 216 a. In an example,remaining germanium of a silicon and germanium layer is condensed into agermanium nanowire channel. In an example, the first germanium nanowirechannel 206 a and the second germanium nanowire channel 210 a are formedsuch that a space of about 5 nm or greater is between the firstgermanium nanowire channel 206 a and the second germanium nanowirechannel 210 a so that interfacial layer material, high-k dielectriclayer material, or titanium nitride capping layer material can be formedaround the first germanium nanowire channel 206 a and the secondgermanium nanowire channel 210 a. In this way, the first silicon andsilicon germanium stack 220 or other silicon and silicon germaniumstacks are oxidized 402 to form germanium nanowire channels.

At 110, silicon oxide, such as a silicon oxide region, is removed, asillustrated in embodiment 500 of FIG. 5. That is, silicon oxide isremoved to expose the germanium nanowire channels, and to form a regionwithin which a gate structure can be formed. In an example, the firstsilicon oxide region 218 a, the second silicon oxide region 208 a, thethird silicon oxide region 212 a, the fourth silicon oxide region 216 a,or other silicon oxide, such as silicon oxide formed from oxidizing 402silicon germanium layers, are removed by an etching process 502.Germanium nanowire channels, such as the first germanium nanowirechannel 206 a, the second germanium nanowire channel 210 a, the thirdgermanium nanowire channel 214 a, or other germanium nanowire channels,can be formed according to various configurations, shapes, or sizes,such as a first germanium nanowire channel 206 b having a cylindricalconfiguration, a second germanium nanowire channel 210 b having thecylindrical configuration, and a third germanium nanowire channel 214 bhaving the cylindrical configuration. In this way, source regions, drainregions, and germanium nanowire channels are formed for a first nanowiretransistor 504, a second nanowire transistor 506, or other PMOS nanowiretransistors.

In an example, a first interfacial layer 606 is formed around the firstgermanium nanowire channel 206 b, a second interfacial layer 610 isformed around the second germanium nanowire channel 210 b, and a thirdinterfacial layer 614 is formed around the third germanium nanowirechannel 214 b, as illustrated in embodiment 600 of FIG. 6. Aninterfacial layer is formed to improve adhesion between materials orlayers. In an example, an interfacial layer comprises nitride, oxide, orother suitable material. In an example, a first high-k dielectric layer604 is formed around the first interfacial layer 606, a second high-kdielectric layer 608 is formed around the second interfacial layer 610,and a third high-k dielectric layer 612 is formed around the thirdinterfacial layer 614, as illustrated in embodiment 600 of FIG. 6. In anexample, a titanium nitride capping layer is formed around one or morehigh-k dielectric layers. In an example, a barrier, such as TaN or TiNis formed around the titanium nitride capping layer.

At 112, a first gate structure 602 is formed around the first germaniumnanowire channel 206 b, to form the first nanowire transistors 504, asillustrated in embodiment 600 of FIG. 6. In an example, the first gatestructure 602 comprises TiN or W, alone or in combination. In theillustrated example, given that there are three germanium nanowirechannels, the first gate structure is also formed around the secondgermanium nanowire channel 210 b, and the third germanium nanowirechannel 214 b. In an example, the first gate structure 602 is formed asa gate-all-around structure surrounding the germanium nanowire channelsto increase gate control, as illustrated in embodiment 600 of FIG. 6. Inanother example, a first gate structure 706 is formed around one or moresurfaces of the germanium nanowire channels, as illustrated inembodiment 700 of FIG. 7. For example, a first interfacial layer 704 isformed around the first germanium nanowire channel 206 b, the secondgermanium nanowire channel 210 b, and the third germanium nanowirechannel 214 b. A high-k dielectric layer 702 is formed around the firstinterfacial layer 704. The first gate structure 706 is formed around thehigh-k dielectric layer 702. In this way, the first gate structure 706is formed around some, but not all, surfaces of the germanium nanowirechannels, which can increase channel density within the first nanowiretransistor 504. The first nanowire transistor 504, the second nanowiretransistor 506, or other nanowire transistor within the semiconductorarrangement 250 are formed as PMOS transistors, where germanium nanowirechannels are formed as P channels for the PMOS transistors. In anexample, a first interlayer dielectric is formed over one or more sourceregions and a second interlayer dielectric is formed over one or moredrain regions. In this way, gate structures are formed between the firstinterlayer dielectric and the second interlayer dielectric. In anexample, a blocking layer is formed below the germanium nanowirechannels to mitigate punch through or leakage.

In an example, one or more NMOS transistors are formed within thesemiconductor arrangement 250 before, during, and/or after formation ofthe one or more PMOS transistors as a single fabrication process becauseformation of NMOS transistors and formation of PMOS transistors bothutilize silicon and silicon germanium stacks. For example, during atleast some of the processes of forming the PMOS transistors, NMOSportion of the semiconductor arrangement 250 are protected by a hardmask. During at least some of the processes of forming the NMOStransistors, PMOS portions of the semiconductor are protected by a hardmask.

FIGS. 8-10 illustrate embodiments of forming one or more NMOStransistors within the semiconductor arrangement 250 utilizing siliconand silicon germanium stacks. In an example, the first nanowiretransistor 504, the second nanowire transistor 506, or other nanowiretransistors formed as PMOS transistors within the semiconductorarrangement 250 are protected by a hard mask during formation of the oneor more NMOS transistors.

In an example, a third silicon and silicon germanium stack 820, a fourthsilicon and silicon germanium stack 822, or other silicon and silicongermanium stacks are formed over the substrate 202, as illustrated inembodiment 800 of FIG. 8. The third silicon and silicon germanium stack820 comprises one or more silicon layers and one or more silicongermanium layers. For example, the third silicon and silicon germaniumstack 820 comprises a first silicon layer 818, a first silicon germaniumlayer 806, a second silicon layer 808, a second silicon germanium layer810, a third silicon layer 812, and a third silicon germanium layer 814.It is appreciated that any number of silicon layers or silicon germaniumlayers can be formed.

A third source region 902 is formed on a first side of the third siliconand silicon germanium stack 820 and a third drain region 904 is formedon a second side of the third silicon and silicon germanium stack 820,as illustrated in embodiment 900 of FIG. 9. In an example, a fourthsource region 906, a fourth drain region 908, or other source and drainregions are formed adjacent to silicon and silicon germanium stacks.Silicon germanium layers within the silicon and silicon germanium stacksare removed to form silicon nanowire channels between source regions anddrain regions, as illustrated in embodiment 1000 of FIG. 10. In anexample, the first silicon germanium layer 806 is removed to form afirst space 806 a between a first silicon nanowire channel 818 a and asecond silicon nanowire channel 808 a, the second silicon germaniumlayer 810 is removed to form a second space 810 a between the secondsilicon nanowire channel 808 a and a third silicon nanowire channel 812a, and the third silicon germanium layer 814 is removed to form a thirdspace 814 a between the third silicon nanowire channel 812 a and thesubstrate 202. In an example, a chemical etch 1002 is performed toremove the silicon germanium layers from the silicon and silicongermanium stacks. In an example, the silicon nanowire channels can beformed according to various configurations, shapes, or sizes, such ascylindrical shapes. For example, an oxidation technique or a hydrogenannealing technique is performed to smooth the silicon nanowirechannels. In an example, gate structures are formed around the siliconnanowire channels to form a third nanowire transistor 1004, a fourthnanowire transistor 1006, or other NMOS nanowire transistors, notillustrated.

In an example, an interfacial layer is formed around one or more of thesilicon nanowire channels. In an example, a high-k dielectric layer isformed around one or more of the silicon nanowire channels or around aninterfacial layer if present. A gate structure may be formed as agate-all-around structure, or around fewer than all sides of a siliconnanowire channel. In an example, the gate structure comprises TiN or W,alone or in combination. Formation of one or more of such gatestructures, interfacial layers or high-k dielectric layers is inaccordance with that described above with regard to formation of a PMOStransistor, according to some embodiments. In an example, a titaniumnitride capping layer is formed around one or more high-k dielectriclayers. In an example, a barrier, such as TaN, TiAlC, TaAlC, or TiAl isformed around the titanium nitride capping layer. In an example, gateheight for a PMOS nanowire transistor is less than a gate height for anNMOS nanowire transistor. In this way, NMOS transistors and PMOStransistors are formed within the semiconductor arrangement 250utilizing silicon and silicon germanium stacks.

FIG. 11 illustrates an embodiment 1100 of an NMOS gate height 1108 and aPMOS gate height 1114. A third nanowire transistor 1004 comprises anNMOS transistor. The third nanowire transistor 1004 comprises a thirdsource region 902 and a third drain region 904 formed over a substrate202. The third nanowire transistor 1004 comprises a first siliconnanowire channel 818 a, a second silicon nanowire channel 808 a, and athird silicon nanowire channel 812 a formed between the third sourceregion 902 and the third drain region 904. A first interlayer dielectric1104 is formed over the third source region 902, and a second interlayerdielectric 1106 is formed over the third drain region 904. A gatestructure 1102 is formed around the first silicon nanowire channel 818a, the second silicon nanowire channel 808 a, and the third siliconnanowire channel 812 a. The gate structure 1102 has an NMOS gate height1108.

A first nanowire transistor 504 comprises a PMOS transistor. The firstnanowire transistor 504 comprises a first source region 302 and a firstdrain region 304 formed over the substrate 202. The first nanowiretransistor 504 comprises a first germanium nanowire channel 206 b, asecond germanium nanowire channel 210 b, and a third germanium nanowirechannel 214 b formed between the first source region 302 and the firstdrain region 304. A third interlayer dielectric 1110 is formed over thefirst source region 302, and a fourth interlayer dielectric 1112 isformed over the first drain region 304. A first gate structure 706 isformed around the first germanium nanowire channel 206 b, the secondgermanium nanowire channel 210 b, and the third germanium nanowirechannel 214 b. The first gate structure 706 has a PMOS gate height 1114.In an example, the PMOS gate height 1114 is less than the NMOS gateheight 1108. For example, the PMOS gate height 1114 is less than theNMOS gate height 1108 due to double metal gate CMP used for PMOS.

In an embodiment, a silicon nanowire to substrate distance 1150 is thesame as a germanium nanowire to substrate distance 1152, where thesilicon nanowire to substrate distance 1150 is not limited to beingrelative to the third silicon nanowire channel 812 a and the germaniumnanowire to substrate distance 1152 is not limited to being relative tothe third germanium nanowire channel 214 b. In an embodiment, thesilicon nanowire to substrate distance 1150 is larger than the germaniumnanowire to substrate distance 1152. In an embodiment the siliconnanowire to substrate distance 1150 is between about 1 nm to about 10 nmlarger than the germanium nanowire to substrate distance 1152. In anembodiment, at least one of thermal annealing, gate dielectricformation, or threshold voltage adjustment associated with forming aPMOS transistor comprising a germanium nanowire channel can be performedconcurrently or substantially concurrently with at least one of thermalannealing, gate dielectric formation, or threshold voltage adjustmentassociated with forming a NMOS transistor comprising a silicon nanowirechannel.

According to an aspect of the instant disclosure, a semiconductorarrangement is provided. The semiconductor arrangement comprises a firstnanowire transistor, such as a PMOS transistor. The first nanowiretransistor comprises a first germanium nanowire channel formed between afirst source region and a first drain region. The first nanowiretransistor comprises a first gate structure formed around the firstgermanium nanowire channel. The semiconductor arrangement comprises asecond nanowire transistor, such as an NMOS transistor. The secondnanowire transistor comprises a first silicon nanowire channel formedbetween a second source region and a second drain region

According to an aspect of the instant disclosure, a method for forming asemiconductor arrangement is provided. The method comprises forming afirst silicon and silicon germanium stack over a substrate. The firstsilicon and silicon germanium stack comprises a first silicon layer anda first silicon germanium layer. A first source region is formedadjacent to a first side of the first silicon and silicon germaniumstack. A first drain region is formed adjacent to a second side of thefirst silicon and silicon germanium stack. The first silicon and silicongermanium stack is oxidized to form a first germanium nanowire channel.The oxidizing comprises transforming the first silicon layer and siliconof the first silicon and germanium layer into a silicon oxide region.The first germanium nanowire channel is formed between the first sourceregion and the first drain region. The silicon oxide region is removed.A first gate structure is formed around the first germanium nanowirechannel to form a first nanowire transistor. A second nanowiretransistor comprising a first silicon nanowire channel is formed withinthe semiconductor arrangement.

According to an aspect of the instant disclosure, a semiconductorarrangement is provided. The semiconductor arrangement comprises a PMOSnanowire transistor. The PMOS nanowire transistor comprises a firstgermanium nanowire channel formed between a first source region and afirst drain region. The PMOS nanowire transistor comprises a first gatestructure formed around the first germanium nanowire channel. Thesemiconductor arrangement comprises an NMOS nanowire transistor. TheNMOS nanowire transistor comprises a first silicon nanowire channelformed between a second source region and a second drain region. TheNMOS nanowire transistor comprises a second gate structure formed aroundthe first silicon nanowire channel.

Although the subject matter has been described in language specific tostructural features or methodological acts, it is to be understood thatthe subject matter of the appended claims is not necessarily limited tothe specific features or acts described above. Rather, the specificfeatures and acts described above are disclosed as embodiment forms ofimplementing at least some of the claims.

Various operations of embodiments are provided herein. The order inwhich some or all of the operations are described should not beconstrued to imply that these operations are necessarily orderdependent. Alternative ordering will be appreciated given the benefit ofthis description. Further, it will be understood that not all operationsare necessarily present in each embodiment provided herein. Also, itwill be understood that not all operations are necessary in someembodiments.

It will be appreciated that layers, features, elements, etc. depictedherein are illustrated with particular dimensions relative to oneanother, such as structural dimensions or orientations, for example, forpurposes of simplicity and ease of understanding and that actualdimensions of the same differ substantially from that illustratedherein, in some embodiments. Additionally, a variety of techniques existfor forming the layers features, elements, etc. mentioned herein, suchas etching techniques, implanting techniques, doping techniques, spin-ontechniques, sputtering techniques such as magnetron or ion beamsputtering, growth techniques, such as thermal growth or depositiontechniques such as chemical vapor deposition (CVD), physical vapordeposition (PVD), plasma enhanced chemical vapor deposition (PECVD), oratomic layer deposition (ALD), for example.

Further, unless specified otherwise, “first,” “second,” or the like arenot intended to imply a temporal aspect, a spatial aspect, an ordering,etc. Rather, such terms are merely used as identifiers, names, etc. forfeatures, elements, items, etc. For example, a first channel and asecond channel generally correspond to channel A and channel B or twodifferent or two identical channels or the same channel.

Moreover, “exemplary” is used herein to mean serving as an example,instance, illustration, etc., and not necessarily as advantageous. Asused in this application, “or” is intended to mean an inclusive “or”rather than an exclusive “or”. In addition, “a” and “an” as used in thisapplication are generally to be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Also, at least one of A and B or the like generally means A or Bor both A and B. Furthermore, to the extent that “includes”, “having”,“has”, “with”, or variants thereof are used, such terms are intended tobe inclusive in a manner similar to “comprising”.

Also, although the disclosure has been shown and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others skilled in the art based upon a reading andunderstanding of this specification and the annexed drawings. Thedisclosure includes all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described components(e.g., elements, resources, etc.), the terms used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure. In addition, while aparticular feature of the disclosure may have been disclosed withrespect to only one of several implementations, such feature may becombined with one or more other features of the other implementations asmay be desired and advantageous for any given or particular application.

What is claimed is:
 1. A semiconductor arrangement, comprising: a first nanowire transistor comprising: a first nanowire channel formed between a first source region and a first drain region; a second nanowire channel formed between the first source region and the first drain region; and an interfacial layer at least partially surrounding the first nanowire channel and the second nanowire channel, wherein the interfacial layer pinches off a space between the first nanowire channel and the second nanowire channel.
 2. The semiconductor arrangement of claim 1, wherein the second nanowire channel overlies the first nanowire channel.
 3. The semiconductor arrangement of claim 1, wherein the first nanowire channel comprises germanium.
 4. The semiconductor arrangement of claim 1, wherein the second nanowire channel comprises germanium.
 5. The semiconductor arrangement of claim 1, comprising: a gate dielectric at least partially surrounding the interfacial layer; and a gate electrode at least partially surrounding the gate dielectric.
 6. The semiconductor arrangement of claim 1, wherein the interfacial layer comprises at least one of an oxide or a nitride.
 7. The semiconductor arrangement of claim 1, comprising: a second nanowire transistor comprising a third nanowire channel, wherein: a substrate underlies the first nanowire transistor and the second nanowire transistor, a distance between a surface of the substrate and a bottom surface of the first nanowire channel is different than a distance between the surface of the substrate and a bottom surface of the third nanowire channel.
 8. The semiconductor arrangement of claim 7, wherein the first nanowire channel comprises a different material composition than the third nanowire channel.
 9. The semiconductor arrangement of claim 1, wherein: the interfacial layer is in contact with an outer perimeter of the first nanowire channel, and the semiconductor arrangement comprises: a gate dielectric separated from the first nanowire channel by the interfacial layer.
 10. A method for forming a semiconductor arrangement, comprising: forming a first stack comprising a first layer having a first composition and a second layer having a second composition; applying oxygen to the first stack to oxidize the first stack; etching the first stack, after being oxidized, to remove the first layer, wherein at least a portion of the second layer forms a first nanowire channel; and forming a first gate structure at least partially surrounding the first nanowire channel.
 11. The method of claim 10, wherein the second layer comprises germanium and applying the oxygen to the first stack comprises pushing the germanium inwardly to concentrate the germanium in a center region of the second layer.
 12. The method of claim 10, comprising: forming an interfacial layer at least partially surrounding the first nanowire channel prior to forming the first gate structure.
 13. The method of claim 10, comprising: forming a second stack comprising the first layer and the second layer; masking the second stack prior to applying the oxygen to the first stack; unmasking the second stack after etching the first stack; masking the first stack; and etching the second stack while the first stack is masked to remove the second layer from the second stack.
 14. The method of claim 13, comprising: annealing the first layer of the second stack after etching the second stack to form a second nanowire channel; and forming a second gate structure at least partially surrounding the second nanowire channel.
 15. The method of claim 14, wherein: annealing the first layer comprises changing a surface profile of the first layer.
 16. A method for forming a semiconductor arrangement, comprising: forming a first stack comprising a first layer having a first composition and a second layer having a second composition; etching an isolation structure adjacent the first stack to expose the first layer and the second layer; etching the first stack, after the first layer and the second layer are exposed, to remove the first layer, wherein at least a portion of the second layer forms a first nanowire channel; and forming a first gate structure at least partially surrounding the first nanowire channel.
 17. The method of claim 16, comprising: applying oxygen to the first stack to oxidize the first stack prior to etching the first stack.
 18. The method of claim 16, wherein: the first stack comprises a third layer having the first composition and a fourth layer having the second composition, the third layer is between the second layer and the fourth layer, etching the isolation structure comprises exposing the third layer and the fourth layer, etching the first stack comprises removing the third layer, wherein at least a portion of the fourth layer forms a second nanowire channel; and the method comprises: forming an interfacial layer, wherein the interfacial layer pinches off a space between the first nanowire channel and the second nanowire channel.
 19. The method of claim 18, wherein forming the first gate structure comprises forming the first gate structure to at least partially surround the interfacial layer.
 20. The method of claim 16, comprising: growing a source/drain region to contact the first layer and the second layer prior to etching the first stack. 